The present invention relates to internal combustion engines having a fuel tank and shroud. More specifically, the field of the invention is that of small air cooled internal combustion engines with a combination plastic fuel tank and shroud.
In internal combustion engine requires a fuel tank, which can be made of metal and bolted to the engine. However, a metal fuel tank is often expensive. Also, the engine should be protected by a shroud which can also lessen the amount of noise and vibration transmitted by the engine and serves to channel air over the engine. In many applications including lawn mowers, the fuel tank and shroud are unitary and made of plastic, which is significantly less expensive than metal. However, the attachment of a plastic fuel tank and shroud is difficult and causes additional cost.
One means of attaching a fuel tank and shroud involves mounting them directly on the engine with screws. While direct screw mounting is easy and inexpensive, the plastic eventually fails. The failure may be due to fatigue, or to the screw loosening and falling out due to the normal vibration of the engine and the extrusion of plastic from beneath the screw heads. To securely attach the fuel tank or shroud to the crankcase, additional brackets or fasteners are used to retain the fuel tank and shroud to the engine structure, and additional retainers such as straps are used to mount the plastic components. These additional brackets, fasteners, and retainers add to the complexity and cost of the engine. Further, fuel tanks and shrouds with these attaching devices require a strong grade of plastic to withstand the engine vibration.
What is needed is a fuel tank and shroud which are attached to the engine more simply and economically. Also needed is a fuel tank and shroud which can be fabricated from less expensive materials.